Field of the Invention
The present invention relates to a fuel cell module including a flat plate stack type fuel cell stack formed by stacking a plurality of flat plate type fuel cells for performing power generation by electrochemical reactions of a fuel gas and an oxygen-containing gas.
Description of the Related Art
In general, a solid oxide fuel cell (SOFC) employs a solid electrolyte. The solid electrolyte is an oxide ion conductor such as stabilized zirconia. The solid electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly, for example, a membrane electrode assembly (MEA). The electrolyte electrode assembly is sandwiched between separators (bipolar plates). In use, generally, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack.
In the SOFC, since the operating temperature is relatively high, the stacked fuel cells need to be heated to the desired temperature beforehand. It is because, if a hot gas is supplied to fuel cells having a low temperature, cracks, etc. may occur in the fuel cells undesirably, due to the large temperature difference.
In this regard, for example, an indirect internal reforming type SOFC disclosed in Japanese Laid-Open Patent Publication No. 2009-059658 (hereinafter referred to as conventional technique 1) is known. In this indirect internal reforming type SOFC, as shown in FIG. 13, a reformer having a first reforming unit 1a and a second reforming unit 2a is provided. The first reforming unit 1a and the second reforming unit 2a are connected in series.
The indirect internal reforming type SOFC includes an SOFC 3a for performing power generation using a reformed gas obtained by a reformer. The SOFC 3a is placed in a casing 4a. The first reforming unit 1a and the second reforming unit 2a are parts of the casing 4a. 
The SOFC 3a has a flame forming unit 5a. The frame forming unit 5a combusts an anode off gas to produce flames 6a. According to the disclosure, the second reforming unit 2a can utilize combustion heat from the flame forming unit 5a, and the first reforming unit 1a can utilize radiation heat from the SOFC 3a. 
Further, a fuel cell module disclosed in Japanese Laid-Open Patent Publication No. 2011-129280 (hereinafter referred to as conventional technique 2) is known. As shown in FIG. 14, in this fuel cell module, a fuel stack 2b, a reformer 3b, and a manifold 4b are surrounded by a lower heat insulating member 5b and a side heat insulating member 6b. In this state, these components are placed in a casing 1b. 
In the fuel cell stack 2b, a high temperature conductive member 7b is provided to contact a lateral end of each fuel cell. The heat conductivity of the high temperature conductive member 7b is higher than the heat conductivity of each fuel cell. Therefore, according to the disclosure, it is possible to suppress occurrence of non-uniform temperature distribution in the fuel cell stack 2b, in the stacking direction of the fuel cells and in the vertical direction.
Further, in a fuel cell system disclosed in Japanese Laid-Open Patent Publication No. 2011-113934 (hereinafter referred to as conventional technique 3), as shown in FIG. 15, a fuel cell 1c which performs power generation by supplied fuel gas and oxygen-containing gas is placed in a heat insulating container 2c. In the heat insulating container 2c, an exhaust gas channel 3c for discharging an exhaust gas discharged from the fuel cell 1c is provided.
An oxygen-containing gas heat exchanger 4c and a vaporizer 5c are provided in the exhaust gas channel 3c along a flow direction of the exhaust gas. Further, a burner 6c for heating at the time of starting operation of the fuel cell 1c or the like is provided between the oxygen-containing gas heat exchanger 4c and the vaporizer 5c. A raw material gas, i.e., a mixed gas of water vapor and a methane gas heated beforehand by the vaporizer 5c is supplied to a reformer 7c. 